1. Field of Technology
The present invention relates to a stepping motor controller for controlling a stepping motor for driving various loads and a stepping motor control program for operating the stepping motor.
2. Description of Related Art
In recent years, as various drive sources, a stepping motor has been widely used. The stepping motor has advantages such that the amount of movement is proportional to the driving pulse number, and the motor is congenial to a digital control circuit, and no feed back circuit is necessary, so that it finds wide applications in various fields.
On the other hand, when the load is excessively high and the pulse frequency is excessively high, a phenomenon that the phase is not switched normally, and asynchronism occurs, and the control is disordered may occur. Further, this state is referred to “step-out”.
Further, in Unexamined Japanese Patent Application Publication 2004-215440 (JPA2004-215440), a countermeasure for the aforementioned step-out is disclosed.
In the invention described in JPA2004-215440, the stepping motor is equipped with an encoder, and by comparison of the actual rotation state of the stepping motor with the driving pulse, the step-out is detected.
And, when the step-out is detected, the controller retains the rotational speed, at the point of time when the step-out is eliminated, returns to the ordinary control, and performs a recovery process for recovering a delay or an excessive advance.
Here, if step-out occurs when the stepping motor is controlled in the self-returnable area (self-starting area), the stepping motor can be recovered by applying the aforementioned control.
However, in the high-speed drive state, the phase is switched quickly and a problem arises that even if the same rotational speed is retained, it is difficult to escape from the step-out state. Further, also in a case of a sudden load variance, an escape from the step-out state may be difficult similarly.
One of the objectives of the present invention is to solve the aforementioned problem and to realize a stepping motor controller and a stepping motor control program for preventing the controller, at time of driving, from falling into an unrecoverable step-out state.